Various polymeric materials have been proposed as binders for high-energy materials, such as solid propellants, explosives, gasifiers of the like. A variety of elastomeric materials have found specific applications in high-energy compositions. Binders are elastomeric materials which spatially immobilize particulates of high-energy material, including fuel material particulates and oxidizer particulates. In many cases, the propellant or explosive formulation also includes a high-energy liquid plasticizer, particularly nitrate ester plasticizers such as nitroglycerin (NG), butane triol trinitrate (BTTN), and trimethylolethane trinitrate (TMETN). High-energy plasticizers contribute to the elastomeric properties of the binder and also contribute to the energy value of the propellant or explosive system. If the propellant or explosive formulation includes a plasticizer, the binder selected must be compatible with the plasticizer in order to spatially immobilize the same; that is, ensure that the plasticizer does not flow and settle from the high-energy composition.
One type of polymeric material commonly used to produce binders is unsaturated hydrocarbon polymers, such as polybutadiene. Although hydrocarbon binders are inherently relatively high in energy, they do not retain nitrate esters; and therefore, propellants having hydrocarbon binders are generally characterized as having relatively low energy. Propellants having hydrocarbon binders are further characterized by relatively low burning rate slopes, relatively low temperature sensitivities and relatively low hazards sensitivities. Hydrocarbon binders are typically loaded with high solids (fuel and oxidizer) content.
Binders based upon polyethers or polyesters, such as polycaprolactone (PCP), retain nitrate esters; therefore, propellants can be produced from these binders having relatively high energies. Ether and, particularly, ester bonds, however, inherently reduce the energy of these binder systems. Thus, a propellant material including a PCP binder may have a high energy, primarily due to the high retention of nitrate ester plasticizer by the PCP elastomeric material, in spite of the inherently relatively low energy of the PCP elastoxer. Propellants having nitrate ester-plasticized polyether or Polyester binders are further characterized by relatively high burning rate slopes, relatively high temperature sensitivities and relatively high hazard sensitivities.
It is a continuing goal to provide higher energy binder systems for high-energy materials, particularly propellants. Furthermore, specific propellant or explosive applications optimally require particular combinations of characteristics, e.g., burn rate slopes, temperature sensitivities and hazards sensitivities, and the need exists for binders which can be used to tailor propellant or explosive formulations to the optimal requirements of specific applications.